Field Emission to control nanometer tip-medium distances in probe storage

In this work, we present a novel concept for high resolution proximity sending based on field emission and provide more insight in the vacuum conditions and electronics needed for stable operation

Spatial transformations of diffusion tensor magnetic resonance images

The authors address the problem of applying spatial transformations (or “image warps”) to diffusion tensor magnetic resonance images. The orientational information that these images contain must be handled appropriately when they are transformed spatially during image registration. The authors present solutions for global transformations of three-dimensional images up to 12-parameter affine complexity and indicate how their methods can be extended for higher order transformations. Several approaches are presented and tested using synthetic data. One method, the preservation of principal direction algorithm, which takes into account shearing, stretching and rigid rotation, is shown to be the most effective. Additional registration experiments are performed on human brain data obtained from a single subject, whose head was imaged in three different orientations within the scanner. All of the authors' methods improve the consistency between registered and target images over naive warping algorithms

Algebras of compact operators

The purpose of this thesis is to examine certain classes of hounded linear operators on a Banach space X in an algebraic light, i.e. as elements of a Banach algebra rather than as operators on X, the Banach algebra in general being the algebra B(X) of all bounded linear operators on X. We choose those properties which can be expressed in general algebraic terms, and then study elements of a general Banach algebra which satisfy these properties. The class originally chosen, suggested to me by Professor P. P. Bonsall, was the class of compact operators on X. As the algebraic properties of such operators generally involve their spectral properties, it was natural to extend our study to include Riesz operators as well

Conjugated Polymer Nanoparticles toward In Vivo Theranostics – Focus on Targeting, Imaging, Therapy, and the Importance of Clearance

Conjugated polymer nanoparticles are highly fluorescent colloids with tunable emission colors ranging from the visible deep into the near infrared spectrum. Conjugated polymer nanoparticles are easy to prepare, tunable in their size, and virtually nonbleachable. Conjugated polymer particles can also be designed to give off heat upon irradiation. All these properties make conjugated polymer particles ideal materials for biomedical fluorescence and photoacoustic imaging as well as for theranostic applications. Here, different examples of surface functionalization to attach pathological homing devices, imaging modalities, as well as the emerging possibilities for therapeutic measures are discussed. Furthermore, clearance of the particles is considered, which is important to ultimately apply the materials for in vivo theranostics. Due to the conjugated backbone of the conjugated polymers, established degradation strategies, as known from hydrophilic nonconjugated polymer carriers, cannot be applied. Bioinspired strategies and potential pathways for degradation and clearance via structural changes upon triggers such as pH, oxidation, and temperature are also discussed in this progress report. © 2017 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Transverse instability and its long-term development for solitary waves of the (2+1)-Boussinesq equation

The stability properties of line solitary wave solutions of the (2+1)-dimensional Boussinesq equation with respect to transverse perturbations and their consequences are considered. A geometric condition arising from a multi-symplectic formulation of this equation gives an explicit relation between the parameters for transverse instability when the transverse wavenumber is small. The Evans function is then computed explicitly, giving the eigenvalues for transverse instability for all transverse wavenumbers. To determine the nonlinear and long time implications of transverse instability, numerical simulations are performed using pseudospectral discretization. The numerics confirm the analytic results, and in all cases studied, transverse instability leads to collapse.Comment: 16 pages, 8 figures; submitted to Phys. Rev.

Late Pleistocene Glaciation in the Mosquito Range, Colorado, U.S.A.: Chronology and Climate

New cosmogenic 10Be surface exposure ages from seventeen moraine boulders in the Mosquito Range suggest that glaciers were at their late Pleistocene (Pinedale) maximum extent at ~21–20 ka, and that ice recession commenced prior to ~17 ka. These age limits suggest that the Pinedale Glaciation was synchronous within the Colorado Rocky Mountain region. Locally, the previous (Bull Lake) glaciation appears to have occurred no later than 117 ka, possibly ~130 ka allowing for reasonable rock weathering rates. Temperature-index modeling is used to determine the magnitude of temperature depression required to maintain steady-state mass balances of seven reconstructed glaciers at their maximum extent. Assuming no significant differences in precipitation compared to modern values, mean annual temperatures were ~8.1 and 7.5 °C cooler, respectively, on the eastern and western slopes of the range with quantifiable uncertainties of +0.8/–0.9 °C. If an average temperature depression of 7.8 °C is assumed for the entire range, precipitation differences - that today are 15-30% greater on the eastern slope due to the influence of winter/early spring snowfall - might have been enhanced. The temperature depressions inferred here are consistent with similarly derived values elsewhere in the Colorado Rockies and those inferred from regional-scale climate modeling

Perceived levels of physical activity amongst people with Parkinson's: impact of age, gender and geography.

Purpose: 1) To explore perceptions of perceived levels physical activity amongst people with Parkinson's. 2) To identify whether relationships exist between perceived levels of physical activity and age, gender, time since diagnosis and geographical location. 3) To explore the relationship between perceived physical activity level and quality of life. Methods: A convenience sample was recruited via the Parkinson's UK Research Support Network. All members were sent an electronic questionnaire which collected the following information: (i) demographic and clinical data; (ii) perceived physical activity levels measured using the International Physical Activity Questionnaire (IPAQ); (iii) Quality of life (QoL) measured using the EQ-5D. All data was analysed using SPSS. Demographic data was evaluated via simple descriptive statistics; Chi Squared and Spearman's rank correlation coefficients were employed to establish relationships between variables

The singular behavior of massive QCD amplitudes

We discuss the structure of infrared singularities in on-shell QCD amplitudes with massive partons and present a general factorization formula in the limit of small parton masses. The factorization formula gives rise to an all-order exponentiation of both, the soft poles in dimensional regularization and the large collinear logarithms of the parton masses. Moreover, it provides a universal relation between any on-shell amplitude with massive external partons and its corresponding massless amplitude. For the form factor of a heavy quark we present explicit results including the fixed-order expansion up to three loops in the small mass limit. For general scattering processes we show how our constructive method applies to the computation of all singularities as well as the constant (mass-independent) terms of a generic massive n-parton QCD amplitude up to the next-to-next-to-leading order corrections.Comment: version to appear in JHEP (sec. 3 with expanded discussion and appendix with added results

Narrow Stimulated Resonance Raman Scattering and WGM Lasing in Small Conjugated Polymer Particles for Live Cell Tagging and Tracking

Conjugated polymer particles are brightly fluorescing and stable materials for live cell imaging. Combination of conjugated polymers with a whispering gallery mode (WGM) resonator allows laser emission from microscale particles. Once internalized by cells, the mode pattern of the laser emission can be used for tagging and tracking, as each laser spectrum represents a bar code to identify individual cells. However, currently these particle systems are limited by their large size, which might interfere with cellular functions. Here, stimulated resonance Raman scattering (SRRS) in small conjugated polymer microparticles is presented as a new method for generating narrow emission as an alternative to WGM-based laser emission. This opens up spectral range for multiplexing optical readout and multicolor imaging of live cells. The synthesis of monodisperse micrometer-sized poly(fluorene-co-divinylbenzene) particles is discussed and their WGM and SRRS emission are characterized. Finally, how these particles and their emission can be employed in live cell imaging and tagging is showcased. © 2020 The Authors. Advanced Optical Materials published by Wiley-VCH Gmb